Make the service name used by a core deployer configurable

[glyn]

Fixes #200

[codecov-io]

Codecov Report

Merging #214 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #214      +/-   ##
=========================================
- Coverage    8.67%   8.66%   -0.01%     
=========================================
  Files          61      61              
  Lines        4151    4154       +3     
=========================================
  Hits          360     360              
- Misses       3758    3761       +3     
  Partials       33      33

Impacted Files	Coverage Δ
pkg/apis/core/v1alpha1/deployer_types.go	33.33% <ø> (ø)	⬆️
pkg/controllers/core/deployer_controller.go	0% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0489b50...6127438. Read the comment docs.

[scothis]

There are a few cases that need to be handled before this can be merged:

• what if there is an existing service with that name?
• what if the serviceName is set on an existing deployer
• what if the serviceName is removed from an existing deployer